Fire barrier materials (often referred to as firestop materials or fire retardant materials) are used to reduce or eliminate the passage of smoke and flames through openings between walls and floors and the openings caused by through-penetrations (i.e., an opening in a floor or wall which passes all the way through from one room to another) in buildings, such as the voids left by burning or melting cable insulation resulting from fire in a modern office building. Characteristics of fire barrier materials suitable for typical commercial use include flexibility prior to exposure to heat, the ability to insulate and/or expand, and the ability to harden in place upon exposure to fire, i.e. to char sufficiently to deter the passage of heat, smoke, flames, and/or vapors. Although many such materials are available, the industry has long sought better and more effective materials. For example, many commercially available materials protect for only limited periods of time because of poor stability at elevated temperatures. Additionally, these materials do not provide good mechanical strength under high-pressure water sprays as required by ASTM E-814-88, "Standard Test Method For Fire Tests Of Through-Penetration Fire Stops".
Foams, caulks, and putty-like materials are known for use in various fire barrier applications. For example, urea-formaldehyde resin foams are known to be useful for filling gaps between concrete floor slabs and upright curtain walls. Such foams typically require some form of support (e.g., a thin sheet of metal) because the mechanical strength of foams is typically relatively low, and that of a charred foam (i.e., after exposure to a fire) generally is even lower. Intumescent compounds (e.g., expandable graphite and hydrated alkali metal silicate granules incorporating an oxyboron compound) have been used with polymeric binders to form caulks for use in filling narrow (e.g., less than about 2.5 cm) joints or small holes. Such materials can also include crosslinking and/or fire retardant compounds (e.g., phosphates), thickeners (e.g., cellulose), and fillers (e.g., inorganic fibers, cellulosic fibers, and polymeric fibers). These compositions, however, are typically flowable and, therefore, generally not capable of maintaining their shape prior to being charred without some type of support. That is, most of these compositions are generally not self-supporting.
Self-supporting fire barrier materials are known. For example, elastomeric sheets containing intumescent compounds are known for use in pipe wraps or cable tray wraps. Also, rigid boards containing polymeric foams in combination with alkali metal silicates are known for use as thermal insulating covers on surfaces such as walls, ceilings, doors, and the like. These rigid foam boards typically are coated with a protective layer to render them moisture resistant. Intumescent ceramic insulating fiber felts or mats are also known; if such felts are used in a space which is not enclosed, such as a curtainwall or a wall penetration, they will often crumble and fall out when heated and expanded.
One approach to answering this need for a self-supporting fire barrier material is described in WO 97/13823 (Landin et al.) wherein a flexible fire barrier felt is formed from an organic polymeric binder, organic fibers having pendant hydroxyl groups, a heat absorbing compound and a phosphorus-containing compound. This material is self-supporting and forms a self-supporting char if exposed to heat and/or flame.
There is still a need in the art, however, for fire barrier materials that are self-supporting and form strong, self-supporting chars upon exposure to heat, which are easy to install, and which are even more economical to produce.